1. Field of the Invention
The present invention relates generally to an audio and video communication system, and in particular, to an apparatus and method for indicating an error state of a transport packet in an audio and video communication system.
2. Description of the Related Art
A Moving Picture Experts Group 2-Transport Stream (MPEG2-TS) packet, which is defined for audio and video broadcast data transmission, has a fixed length of 188 bytes including a 4-byte header and a 184-byte adaptation field/payload. The header includes a 1-bit Transport_Error_Indicator field indicating either the presence or absence of an error in a Transport Stream (TS) packet. The Transport_Error_Indicator field is set to a value indicating the absence of an error in a transmission from a transmitter. A physical layer of a receiver receiving the TS packet determines the presence or absence of an error, based on the error correction result of a Forward Error Correction (FEC) or the error detection result of a Cyclic Redundancy Check (CRC), sets the Transport_Error_Indicator field to a value indicating the check result, and provides the same to an upper layer.
The CRC for the TS packet may or may not be used. That is, if a CRC for each TS packet is not used, the presence or absence of an error in each TS packet is determined by the receiver, based only on a result of the FEC. However, in this case, the receiver cannot properly know how the presence or absence of an error is determined because the receiver determines the presence or absence of an error in each TS packet depending on an indicated flag value regardless of how the presence or absence of an error is determined.
Further, if a CRC for each TS packet is used, and it is determined that an error correction by FEC fails and there is no error as a result of CRC, or if it is determined that an error correction by FEC succeeds but there is an error as a result of CRC, i.e., when the CRC result and the FEC result provide different indications, the receiver cannot represent the various states.
In processing an AV stream extracted from TS packets, the receiver performs an erasure correction using error information of the TS packets. Therefore, the reliability of an erasure flag is important for correct erasure correction. Accordingly, information about states, such as detection or non-detection of a CRC, a result of a CRC detection and a result of an FEC in the physical layer, should be transmitted accurately.
Accordingly, a need exists for an improved scheme for indicating an error state, such as a result of a CRC detection, as a result of an FEC.